The field of the invention is printed wiring board fabrication.
Printed wiring boards are known electronic component structures which contain copper strips or paths arranged in a conductive pattern on a relatively flat electrically insulative structure or base. The copper strips form current-conducting paths, the electric wiring, by means of which other electrical components thereafter mounted on the board may receive or pass electrical current to other electrical components, similarly mounted, or from a power source. These circuit/wiring boards are notoriously old and well-known, having achieved wide application in all kinds of electronic devices, including radios, televisions, and computers, to name a few.
One wiring board structure is referred to as a two-sided plated through-hole board. The board contains electrical conductors on its front and back surfaces, and at least some of those conductors on opposite sides are electrically inter-connected by means of the plated xe2x80x9cthrough-holexe2x80x9d connections. The through-hole is a hole formed through the board between intercepting conductors on the opposite board sides and the hole wall is plated with metal electrically connecting the two conductors. A number of these wiring boards may be laminated or bonded together to form what is known as a multi-layer printed wiring board, and in such multi-layer wiring board through-holes drilled through the layers after the layers are aligned may form electrical connections to different conductive layers in the bonded stack. A less complex printed wiring board is a single-sided plated through-hole wiring board in which a through-hole is drilled through the board and plated with metal even though a conductor circuit pattern appears on only one board surface.
Unfortunately, increasing the number of layers in a multi-layer board tends to cause difficulties in processing and to reduce yields. In particular, drilling and electro-plating through holes becomes more difficult as layer counts increase. Thus, there is a continuing need for newer assemblies and methods for producing assemblies having lower layer counts.
The present invention is directed to methods and devices relating to the fabrication of wiring boards having a built up layer laminated within the board. More specifically, a preferred printed wiring board (PWB) comprises an inner high density circuit routing component laminated within the wiring board, and plated through holes electrically coupling the inner high density circuit to a conductive pattern located on a surfaces of the PWB. A preferred method for forming such a PWB comprises: providing a high density routing component having an exposed conductive pattern on at least one surface; providing wiring board layers; laminating the high density routing component between the two wiring board layers; electrically connecting a conductive portion of each of the wiring board layers to the high density routing component.
Various objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention, along with the accompanying drawings in which like numerals represent like components.